(1) Field of the Invention
The invention relates to an interface for the concentrated loads introduction into a grid stiffened shell-like fiber reinforced composite structure, particularly a loads interface for a plug type aircraft door with the features of the preamble of claim 1.
(2) Description of Related Art
Especially door fittings of an airplane door are used to transfer load from the door to the airplane fuselage. Said door fittings are part of the primary structure of a typical airplane door. In flight conditions internal pressure is acting on the airplane door and said internal pressure results in transversal loads as concentrated pointed loads at the corresponding contact points between the airplane door and the fuselage side. Supplemental loads rectangular to said transversal loads on the contact points result from friction and inclined door stops. Thus there exists a concentrated multi-axial loading state at the door fitting—and in particular at the load introducing contact points and said concentrated multi-axial loading state needs to be transferred to a background structure of the airplane door.
The document DE 102006054431 A1 discloses a door fitting for the mounting of doors and flaps on the fuselage structure and/or wing structure of an aircraft, with a door holder which has the bearing elements for the door or flap, and with a flange which is used for the fastening to the fuselage structure or wing structure, the door holder and flange being formed as a single part in the form of a flat-surfaced, plate-like component. This state of the art is efficient but does not provide sufficient safety margin against overstressing at the highest loaded door stops. Moreover, said state of the art is focused on pure transversal loads whereas loads in circumferential and longitudinal direction that occur in any real aircraft application cannot be transferred sufficiently in the underlying composite structure.
The document US 2010294888 A1 discloses a panel including a plurality of retainers along its lateral sides, these being intended to engage, in the closure position of the panel, with corresponding retainers located on the frame structure of this panel. The panel includes at least one beam, a longitudinal end portion of which has a slot emerging in the end face of the beam and located at a suitable position for mounting a retainer directly on this beam. The retainer includes a retaining part and a mounting part formed by a base, the mounting part forming one body with the retaining part. The mounting part and the slot are shaped such that the mounting part engages tightly in the slot and the mounting part is fastened to the beam by fastening members, particularly nuts and bolts, which are positioned approximately perpendicular to the principal direction of the beam. US 2010294888 A1 takes into account exclusively forces due to the pressurization.